The proposed work is a continuation of the study of sugar-transport across cell membranes, particularly those in the intestinal epithelium. The nature and function of the sugar-carrier will be explored by studying the transport of synthetic, unnatural sugar derivatives. The possible interaction between the intestinal sodium pump and the uphill transport of sugars will be explored. The sodium pump will be studied by specific inhibitors, by measuring the fluxes of radioactive isotopes and by recording electric activities with the short-circuiting technique. The patho-physiology of malabsorption, the pharmacology and toxicology of sugar-, electrolyte-, and water-transport will be included in this study.